β-Cyclodextrin (β-CD) polymers are promising adsorbents with demonstrated removal performances for per- and polyfluoroalkyl substances (PFASs) from contaminated water sources. Despite their efficacy in PFAS removal, previously studied β-CD polymer platforms are inadequate at addressing fundamental questions regarding PFAS adsorption mechanisms as their adsorbent structures are not well-defined, as well as the side reactions that generally arise due to the randomness of crosslinking chemistries. We redesigned a new, modular and highly porous β-CD polymer by covalently linking styrene groups to β-CD to form a discrete monomer, which is compatible with a myriad of comonomers in a near quantitative radical polymerization. Here, we report a β-CD polymer with cationic functional groups, which achieved nearly 100% removal for a number of 1 µg L<sup>-1</sup> PFASs at an unprecedented adsorbent loading of 1 mg L<sup>-1</sup>. Furthermore, when the adsorbents were studied in a salt matrix, we observed a complementary interplay of hydrophobic and electrostatic interactions for long-chain PFAS adsorption whereas short-chain PFAS primarily relied on electrostatic interaction as the mode of adsorption. These materials exhibited great promise in anionic PFAS removal, and the composition can be tailored to target a wider scope of micropollutants with diverse charges.

Modular porous cyclodextrin polymer platform for anionic PFAS adsorption from water

ACS Spring 2022

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